The ultimate objective of this program is the development of a superior dental adhesive that will not only produce a permanent bond to dentin, but to other tooth substrates and restorative materials such as dental composites. The specific aims of this program are: (1) To identify the optimum unsaturated isocyanate/vinyl monomer compositions and determine their reactivity ratios and Q and e values. (2) To control via reactivity ratios the composition of these proposed vinyl copolymers in terms of the content and distribution of desirable functional groups. (3) To determine the adhesive properties of the copolymers to dentin and enamel substrates and evaluate system modifiers that enhance their adhesion. (4) To ascertain the concentration of isocyanate functionality necessary in the copolymer to obtain a maximum adhesive strength to the dental substrate. (5) To ascertain the residual unsaturation, molecular weight, and molecular weight distribution required by the copolymers to provide maximum polymer strength obtainable with final cure. (6) To determine the physical and mechanical properties of the new copolymers developed on this program as potentially superior dental adhesives. (7) To determine and evaluate the microleakage and marginal gap control of these new dental adhesives. (8) To integrate the results of these studies into a fundamental understanding of adhesive molecular design for optimum performance in the oral environment. This subproject will encompass five major phases. Phase 1 will determine monomer reactivity ratios and accomplish aims 1 and 2. Phase 2 is the design and synthesis of copolymer adhesives addressed in specific aims 3, 4, and 5. For Phase 3 the methodology is proposed for the characterization of physicochemical properties and the significance of these properties is addressed in specific aims 4, 5, and 6. Phase 4 is the determination of dental properties and the further enhancement of the adhesive bond strength through system modifiers in specific aim 7. The final phase will address the specific aim 8 and be a critical assessment of the biocompatibility and performance of candidate copolymer dental adhesives, and the development of a protocol for future clinical studies.